Differential assembly with welded differential carrier

ABSTRACT

A differential assembly includes a differential carrier ( 5 ) with a first carrier part ( 6 ) with a free first annular face ( 13 ) and a second carrier part ( 7 ) connectable to the first carrier part ( 6 ) and having a free second annular face ( 15 ), and a plurality of circumferentially distributed recesses ( 9 ) formed between the two carrier parts ( 6, 7 ); per carrier part ( 6, 7 ), a sideshaft gear ( 22, 23 ) is rotatably supported therein; and a supporting element ( 10 ) with journals ( 12 ) is held in the differential carrier ( 5 ). Each of the journals engages one of the recesses ( 9 ) of the differential carrier ( 5 ) and carries a differential gear ( 19 ) for driving the sideshaft gears ( 22, 23 ). The first and the second carrier part ( 7 ) are welded along a joining region formed between the two annular faces ( 13, 15 ) which is interrupted by the recesses ( 9 ) in the circumferential direction.

The invention relates to a differential assembly which forms part of adifferential drive and, more particularly, serves to be used in thedriveline of a motor vehicle. Such differential assemblies aresufficiently known. They commonly comprise a differential carrier inwhich, on an axis of rotation, there are arranged sideshaft gears which,for torque transmitting purposes, can be connected to associatedsideshafts. The sideshaft gears are driven via differential gears whichrotate together with the differential carrier and which are supported soas to be rotatable around journal axes positioned radially relative tothe axis of rotation.

U.S. Pat. No. 3,202,466 discloses a bevel gear differential with aplurality of differential gears rotating together with the differentialcarrier and sideshaft gears engaging same. The differential gears arerotatably held on radial journals which are inserted into bores of thedifferential carrier. The differential carrier is provided in two parts,with the separating region adjoining the central plane. The two housingparts are connected to one another via a flange connection. A similardifferential assembly is known from EP 0 864 779 B1 wherein the journalscarrying the differential gears are held in longitudinal grooves of thedifferential carrier. In the differential assembly known from WO03/031843 A1, the journals are received in corresponding bearing blockswhich, in turn, engage longitudinal grooves of the differential carrier.

From DE 102 38 236 A1, there is known a differential assembly with atwo-part differential carrier which comprises a dish-shaped carrier partand cover-shaped carrier part. The two carrier parts are connected toone another by laser welding.

DE 2 359 828 shows a differential assembly with a three-partdifferential carrier which comprises two outer parts and an intermediatesleeve part in which the journal is received in corresponding bores. Thetwo carrier parts are connected to one another by electron beam welding.

It is the object of the present invention to propose a differentialassembly, more particularly for being used in the driveline of a motorvehicle, which is compact in design and which, at the same time, can beproduced in a simple and cost-effective way.

The object is achieved by providing a differential assembly, moreparticularly for being used in the driveline of a motor vehicle,comprising a differential carrier which is rotatingly drivable around anaxis of rotation A and which comprises a dish-shaped first carrier partwith a free first annular face and a dish-shaped second carrier partbeing connectable to the first carrier part and having a free secondannular face, wherein a plurality of circumferentially distributedrecesses is formed between the first carrier part and the second carrierpart;

a supporting element held in the differential carrier and having aplurality of journals, wherein each of the journals engages one of therecesses of the differential carrier and rotatably carries adifferential gear for driving two sideshaft gears; wherein the first andthe second carrier part are connected to one another by welding along ajoining region formed between the first annular face and the secondannular face, wherein the weld formed in this way is interrupted by therecesses in the circumferential direction.

This solution allows the differential carrier to be produced without anythreaded connections and without further setting measures and aligningmeasures for the individual components relative to one another. Theindividual components are centred automatically relative to one another,the advantage being that by welding the two carrier parts to oneanother, it is possible to save production and assembly stages, so thatthe overall production costs can be reduced. Because the weld is locatedin the region of the recesses of the differential carrier, thecomplexity of the two carrier parts is negligible.

According to a preferred embodiment, the recesses for receiving thejournals are formed in the first carrier part only, extend from the freefirst annular face in the axial direction and interrupt said firstannular face. This results in a simple design of the second carrier partwhose second annular face is preferably closed continuously.Furthermore, it is proposed that the first carrier part comprises aflange for introducing torque into the differential carrier. This isadvantageous in that the torque can be introduced directly from thefirst carrier part into the supporting element. The weld is positionedoutside the torque flow.

According to a concrete embodiment, the first carrier part and thesecond carrier part are designed in such a way that the weld is arrangedso as to be axially offset relative to the supporting element, with theweld preferably comprising a minimum axial distance from the supportingelement. The axial offset ensures that the second carrier part cancomprise a smooth annular face without any axial cuts. With reference tothe axis of rotation A, the weld is positioned in a radial plane.

According to a preferred embodiment, the second carrier part comprisesan annular recess into which the first carrier part can be introduced bymeans of a cylindrical projection, with centring being effected betweenthe cylindrical projection of the first carrier part and the annularrecess of the second carrier part. In this way it is ensured that thefirst carrier part and the second carrier part are radially centredrelative to one another during assembly.

It is proposed that the first annular face and/or the second annularface are/is conical in shape. This is advantageous in that there isformed a sufficiently large V-gap for the weld. For welding purposes,any standard welding method can be applied. If electron beam or laserwelding is used, the first annular face and the second annular face canalso be positioned in radial planes and abut one another in a planarway.

According to a preferred embodiment, the differential assembly isprovided in the form of a crown gear differential, with the sideshaftgears being provided in the form of crown gears and the differentialgears in the form of spur gears. The first sideshaft gear is rotatablysupported in the first carrier part and serves to transmit torque to afirst sideshaft to be connected. The second sideshaft gear is rotatablysupported in the second carrier part and serves to transmit torque to asecond sideshaft to be connected. Using a crown gear differential isadvantageous in that the forces transmitted from the differential gearsto the crown gears, with reference to the journal axis B, comprise onlya radial force component. There are no axial force components in thedirection of the journal axis B which would have to be accommodated bythe differential carrier. The wear at the contact faces between thedifferential gears and the differential carrier is thus minimised.However, this embodiment does not mean that the inventive differentialassembly is limited to crown gear differentials. On the contrary, theinventive idea can easily be transferred to bevel gear differentialswherein the differential gears and sideshaft gears are provided in theform of bevel gears.

There are preferably provided at least three differential gears, withthe supporting element being centred via the meshing engagement of thedifferential gears and the sideshaft gears on the axis of rotation A.For lubrication purposes, the journals of the supporting elementcomprise flattened portions which extend parallel to the journal axis B.In a preferred embodiment, the journals are held in the recesses withaxial play in the direction of the axis of rotation A, so that thedifferential gears can set themselves centrally between the sideshaftgears. The tooth play of the teeth between the differential gears andthe sideshaft gears can thus be set so as to be symmetric.

According to a preferred embodiment, each of the two sideshaft gearscomprises an axially projecting hub to be able to transmit torque to therespective sideshaft, with the hub partially projecting into a centralaperture of the supporting element, with an annular radial gap beingformed between the hub and the supporting element. The annular gap andthe longitudinal extension of the recesses make it possible for thesupporting element with its differential gears to set itself freelyrelative to the sideshaft gears. This measure permits tolerances to berough, which has a positive effect on the production costs.

According to a further embodiment, at least one of the sideshaft gearsis rotatingly supported in the differential carrier by means of arolling contact bearing. This applies if a sideshaft gear supported inthe differential carrier is connected to an outer joint part of aconstant velocity universal joint. Using a rolling contact bearing atthe sideshaft gear connected to the constant velocity universal joint isadvantageous in that the forces occurring can be introduced into andsupported by the differential carrier. The constant velocity universaljoint is preferably provided in the form of a tripode joint.

Preferred embodiments will be described below with reference to thedrawings wherein

FIG. 1 is a radial view of an inventive differential assembly.

FIG. 2 shows the differential carrier according to FIG. 1 in alongitudinal section.

FIG. 3 is an exploded view of the differential assembly according toFIG. 1 in a longitudinal section.

FIG. 4 shows the differential assembly according to FIG. 3 in alongitudinal section in the finish-assembled condition.

FIG. 5 shows the differential assembly according to FIG. 4 in thebuilt-in condition with a tripode joint.

FIG. 1 shows an inventive differential assembly 2 comprising bearingportions 3, 4 to provide support in a stationary drive housing (notillustrated). The differential assembly 2 serves to transmit torque froma driveshaft in a driveline in a motor vehicle (not illustrated) via twosideshaft gears to an associated sideshaft. FIG. 1 shows the hubs 24, 25connected to the sideshaft gears. The differential assembly 2 comprisesa differential carrier 5 which is rotatable around an axis of rotation Aand which comprises a first carrier part 6 and a second carrier part 7which are welded to one another. The first carrier part 6 comprises anintegrally formed-on flange 8 to which there can be connected a ringgear 11 (shown in FIG. 5 only) for transmitting torque into thedifferential carrier 5. In the first carrier part 6 there are providedaxially extending recesses 9 which can be engaged by a supportingelement 10 by means of its journals 12.

The differential carrier 5 consists of a first carrier part 6 and asecond carrier part 7 and is shown in FIG. 2 in which it is possible tosee the recesses 9 for being engaged by the journals 12 for torquetransmitting purposes. The first carrier part 6 comprises a firstannular face 13 substantially positioned in a radial plane withreference to the axis of rotation A, and an adjoining cylindricalprojection 14. The second carrier part 7 comprises a second annular face15 positioned opposite the first annular face 13, and an adjoiningannular recess 16. For assembly purposes, the second carrier part 6 withits annular recess 16 is slid onto the cylindrical projection 14 of thefirst carrier part 7. The annular recess 16 opposite the cylindricalprojection 14 is designed in such a way that the first and the secondcarrier part 6, 7 are jointly centred on the axis of rotation A. The twoannular faces 15, 16 positioned opposite one another are both slightlyconical so that, between same, there is formed a V-shaped join if viewedin a longitudinal section. The shape of the join depends on the weldingmethod used. After the differential assembly 2 has been produced, theweld 17 is formed in said join. To produce the weld 17 between the firstcarrier part 6 and the second carrier part 7, a welding device (notillustrated) is directed towards the join, and the differential carrier5 is rotated around its axis of rotation A, with the circumferentialregions in which there are provided the recesses 9 being saved.

FIGS. 3 and 4 which will be described jointly below show the entiredifferential assembly. The differential carrier contains the supportingelement 10 which rotates around the longitudinal axis A jointly with thedifferential carrier 5. The supporting element 10 is produced so as tobe integral and comprises a plurality of journals 12 whose journal axesextend perpendicularly to the axis of rotation A; it also comprises acentral aperture 18. The journals 12, which can be provided in anynumber, with four being provided in the present case, are received inthe recesses 9 in the first carrier part 6. On each of the journals 12,there is rotatably supported a differential gear 19, with the bearingbeing a friction bearing. For lubricating the friction bearing, thejournals 12 comprise flattened regions 20 which extend parallel to thejournal axis B. The differential gears 19 are axially movably held onthe associated journal 12.

The first sideshaft gear 22 and the second sideshaft gear 23 are drivenvia the supporting element 10 and the differential gears 19. Thesideshaft gears 22, 23 are each integrally connected to projecting hubs24, 25 which are each rotatably supported in an associated carrier part6, 7, with the hub 24 at the flange end being supported by a rollingcontact bearing 35 in a sleeve-shaped projection 36 of the first carrierpart 6. The hub 25 at the cover end is supported by a friction bearing37 in a sleeve-shaped projection 38 of the second carrier part 7. Thereason for using a rolling contact bearing 35 for supporting the hub 24at the flange end is that said hub 24 is to be connected to a constantvelocity universal joint so that higher forces have to be supported inthe bearing region. This is shown in detail in FIG. 6 which will bedescribed below.

The two sideshaft gears 22, 23 are axially supported against the firstand the second carrier part 6, 7, with friction-reducing abutment discs28, 29 with a radial face each. The differential gears 19 which arefloatingly held on the respective journal 12 are supported via abutmentdiscs 31, 32 against the first carrier part 6 in the radial directionwith reference to the axis of rotation A. The differential assembly 2 isprovided in the form of a crown gear differential, so that thedifferential gears 19 are provided in the form of spur gears and thesideshaft gears 22 in the form of crown gears. Providing thedifferential assembly 2 in the form of a crown gear assembly isadvantageous in that the forces transmitted from the differential gears19 to the crown gears 22, 23 comprise only axial components withreference to the axis of rotation A. There does not occur any radialcomponents which would have to be accommodated by the differentialcarrier 5. The wear between the differential gears 19 and the abutmentdiscs 31, 32 is thus minimised.

The two sideshaft gears 22, 23 each comprise a hub 24, 25 with innerteeth 26, 27 into which it is possible to insert sideshafts (not shown)in a rotationally fast way for torque transmitting purposes. The lengthof the inner teeth 26, 27 and thus the length of the hub 24, 25 dependson the torque to be transmitted and on the diameter of the toothing. Inorder to obtain an axially short differential assembly, the two hubs 24,25 project into the central aperture 18 of the star-shaped supportingelement 10, with the diameter of the aperture 18 having been selected tobe such that there remains an annular gap between the hubs 24, and thecarrying element 10 to enable the supporting element 10 to be freelycentred during assembly on the axis of rotation A. Furthermore, it isthus possible to have rough production tolerances of the hubs 24, 25. Attheir opposed ends, the hubs 24, 25 are closed by cover parts 33, 34which can be produced in the form of formed plate metal parts forexample. The cover parts 33, 34 prevent transmission oil from flowingout of the differential assembly 2 into the toothed region.

For the purposes of assembly which preferably takes place with the axisof rotation extending in the vertical direction, first the sideshaftgear 22 at the flange end is inserted into the sleeve-shaped projection36 of the first carrier part 6, with an abutment disc 28 being arrangedtherebetween. Subsequently, the differential gears 19 are slid on to thejournal 12 of the supporting element 10 and then, the unit consisting ofthe supporting element 10 and the differential gears 19 is inserted intothe first carrier part 6, with the differential gears 19 being made toengage the sideshaft gears 22. Furthermore, the second sideshaft gear 23is placed on to the differential gears 19 and made to engage same.Thereafter, the second carrier part 7 is slid in to the first carrierpart 6, with the abutment disc 29 being arranged therebetween, with thecylindrical projection 14 engaging the annular recess 19 to enable thetwo carrier parts 6, 7 to be centred relative to one another. Finally,the join formed between the first annular face 13 and the second annularface 15 is closed by a weld 17. Before the welding operation takesplace, the first and the second carrier part 6, 7 are axially alignedrelative to one another in such a way that a tooth play is set betweenthe differential gears 19 and the sideshaft gears 22, 23. Any weldingmethod can be used for connecting the two carrier parts 6, 7. Becausethe recesses 9 for receiving the journals 12 are formed in the firstcarrier part 6 only, the second carrier part 7 comprises a simpledesign, with the second annular face 15 of the carrier part 7 beingcontinuously closed. The procedure and expenditure of producing andassembling the inventive differential assembly, in total, are minimised.

FIG. 5 shows the differential assembly 2 in the built in condition witha connected constant velocity joint 39. Such differential assemblieswith a constant velocity joint 39 connected on one side are usedparticularly in drivelines of motor vehicles, having a driveshaft whichis arranged so as to be offset eccentrically with reference to alongitudinal vehicle axis, as is the case, for example, with front wheeldrive motor vehicles with a transversely built in engine. Thedifferential assembly corresponds to that shown in FIGS. 1 to 5, whichis reason why reference is made to the above description.

The differential assembly with its sleeve-shaped projections 36, 38 issupported by rolling contact bearings 41, 42 in a stationary drivehousing 43 and outwardly sealed by seals 44, 45. To the sideshaft gear24 at the flange end there is connected the constant velocity plungingjoint 39 which is provided in the form of a tripode joint. Tripodejoints are known in principle and described in DE 43 14 503 C1 forexample to which reference is hereby made. The plunging joint 39comprises an outer joint part 46 with an integrally formed-on journal 51with teeth which, for torque transmitting purposes, engages the innerteeth 26 of the hub 24 and is axially secured by a securing ring 53. Inaddition to the outer joint part 46, the plunging joint 39 comprises astar-shaped inner joint part 37 with three arms 48 on each of whichthere is rotatably held a roller unit 49. The roller units 49 engagetracks 50 of the outer joint part 46, which extend parallel to the axisof rotation A, for the purpose of transmitting torque to the inner jointpart 47. Into the inner joint part 47 there is inserted a sideshaft 52in a rotationally fast and axially secured way, and the sideshaft 52 isable to carry out angular movements and axial displacement movementsrelative to the outer joint part 46 whose longitudinal axis coincideswith the axis of rotation A of the differential assembly 2. The plungingjoint 39 is sealed relative to the environment by a convoluted boot 54which, with a first collar 55, is sealingly attached to the outer jointpart 46 by means of a clamping strip 56 and which, with a second collar57, by means of a clamping strip 58, is sealingly attached to thesideshaft 52. The first collar 56 is connected to an adapter 53 which,on its radial outside, comprises a cylindrical contour and, on itsradial inside, a trilobar contour adapted to the cross-section of theouter joint part 46. The convoluted boot 54 extends over the annularchamber between the outer joint part 46 and the sideshaft 52, thuspreventing dirt from entering the plunging joint 39 and lubricant fromescaping from the plunging joint 39.

1-16. (canceled)
 17. A differential assembly for use in the driveline of a motor vehicle, comprising: a differential carrier which is rotatingly drivable around an axis of rotation (A) and which comprises a dish-shaped first carrier part with a free first annular face and a dish-shaped second carrier part connectable to the first carrier part and having a free second annular face, wherein a plurality of circumferentially distributed recesses is formed between the first carrier part and the second carrier part; a supporting element held in the differential carrier and having a plurality of journals, wherein each of the journals engages one of the recesses of the differential carrier and rotatably carries a differential gear for driving two sideshaft gears; wherein the first and the second carrier part are connected to one another by welding along a joining region formed between the first annular face and the second annular face, wherein the weld is interrupted by the recesses in the circumferential direction.
 18. A differential assembly according to claim 17, wherein the recesses for receiving the journals are formed in the first carrier part only, extend from the free first annular face in the axial direction and interrupt said first annular face.
 19. A differential assembly according to claim 17, wherein the second annular face of the second carrier part is closed continuously.
 20. A differential assembly according to claim 17, wherein the first carrier part and the second carrier part are designed in such a way that the weld is arranged so as to be axially offset relative to the supporting element.
 21. A differential assembly according to claim 20, wherein the weld comprises a minimum axial distance from the supporting element.
 22. A differential assembly according to claim 17, wherein the second carrier part comprises an annular recess into which the first carrier part can be introduced by a cylindrical projection.
 23. A differential assembly according to claim 22, wherein centering is effected by the cylindrical projection of the first carrier part and the annular recess of the second carrier part.
 24. A differential assembly according to claim 17, wherein the first annular face or the second annular face is conical in shape.
 25. A differential assembly according to claim 17, wherein the first carrier part comprises a flange for introducing torque into the differential carrier.
 26. A differential assembly according to claim 17, wherein the differential assembly is provided in the form of a crown gear differential.
 27. A differential assembly according to claim 17, comprising at least three differential gears, wherein the supporting element is centered on the axis of rotation (A) via a meshing engagement of the differential gears with the sideshaft gears.
 28. A differential assembly according to claim 17, wherein the journals of the supporting element, for lubricating purposes, comprise flattened portions extending parallel to a journal axis (B).
 29. A differential assembly according to claim 17, wherein the journals are held in the recesses so as to be axially movable with reference to the axis of rotation (A).
 30. A differential assembly according to claim 17, wherein each of the two sideshaft gears comprises a hub for transmitting torque to an associated sideshaft which partially projects into a central aperture of the supporting element, wherein a radial gap exists between the respective hub and the supporting element.
 31. A differential assembly according to claim 17, wherein at least one of the sideshaft gears is rotatingly supported in the differential carrier by a rolling contact bearing.
 32. A differential assembly according to claim 31, wherein the sideshaft gear supported by a rolling contact bearing in the differential carrier can be connected to an outer joint part of a constant velocity universal joint. 